Long-Term Debt - Summary of Maturities of Borrowing Obligations (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Sep. 30, 2023
Debt Instrument [Line Items]
2025	$ 87,500
2028	210,000
Total before unamortized discount and issuance costs and current portion	297,500
Less: unamortized discount and issuance costs	(18,610)
Total long-term debt	278,890	$ 275,951
2028 Notes
Debt Instrument [Line Items]
2028	122,500
Total before unamortized discount and issuance costs and current portion	122,500
Less: unamortized discount and issuance costs	(2,041)
Total long-term debt	120,459
2025 Modified Notes
Debt Instrument [Line Items]
2025	87,500
2028	87,500
Total before unamortized discount and issuance costs and current portion	175,000
Less: unamortized discount and issuance costs	(16,569)
Total long-term debt	$ 158,431